This invention relates in general to electrode structures and active matrix liquid crystal displays, and in particular to a wire electrode structure and an active matrix liquid crystal displays employing at least one wire electrode structure for addressing.
The active matrix liquid crystal display (AMLCD), including thin-film transistor liquid crystal display (TFT-LCD) and thin-film diode (e.g. MIM diode) liquid crystal display (TFD-LCD) has been widely used for lap-top computers, small screen televisions and the like. It is currently a mainstream technology of the flat panel display which has a good performance in terms of color gamut, gray scale and resolution.
However, this conventional AMLCD has some limitations and shortcomings. For instance, it is difficult to use the conventional AMLCD for large screen displays, such as those greater than 30 inches diagonally. In addition, it is difficult and costly to manufacture conventional AMLCDs, because of a requirement of many mask steps, high processing cost and high capital investment on equipment involved. Furthermore, conventional AMLCDs usually demonstrate certain drawbacks such as low-brightness and low efficiency due to a low aperture ratio.
In order to overcome the above-described limitations and shortcomings, active matrix liquid crystal displays employing plasma gas discharge addressing have been proposed in the place of thin-film transistor or thin-film diodes. See for example, U.S. Pat. No. 5,214,521 to Kwon et al. As in all AMLCDS, in the device proposed by Kwon et al., light transmittance through liquid crystal (LC) cells is controlled by applying appropriate voltages across a layer of LC material. On one side of the LC layer is an array of electrodes as in the TFT-LCD and TFD-LCD, where each of the electrodes in the array acts as a capacitor plate. On the other side of the layer, however, is a very thin dielectric layer separating the LC layer from an array of gas chambers. By causing plasma gas discharge in the chambers, a surface of the dielectric layer is charged to a desired electrical potential so that such surface acts as a capacitor plate. Such surface of the dielectric layer, together with a matching electrode in the array of electrodes on the other side of the LC layer, then control the light transmittance of the LC cell therebetween.
In order for the above-described plasma gas discharge AMLCD to be feasible, the above-described dielectric layer must be very thin; otherwise, the charges on the surface of the dielectric layer will be ineffective to affect the light transmittance of the LC layer. As described in the '521 patent to Kwon et al., the thin dielectric plate is a thin glass sheet of about 50 microns in thickness.
In order to avoid leakage of the plasma gas in the above-described device proposed by Kwon et al., it is necessary to vacuum seal the gas chambers. Therefore, the above-described thin dielectric layer of Kwon et al. must be able to withstand atmospheric pressure and vacuum sealing. The process for manufacturing a large sheet of very thin glass forming one side of vacuum chambers is very difficult. Furthermore, in order to achieve adequate resolution, the gas chambers for controlling and addressing individual LC cells must be small. In such event, the side walls of the gas chambers would severely limit the aperture ratio of the display, so that only a low percentage of the light from a backlight will be able to penetrate the gas chambers. The display is, therefore, of low efficiency and poor brightness. It is possible to increase the aperture ratio by increasing the size of the gas chamber laterally to the display. This, on the other hand, has the undesirable effect of reducing the resolution of the display. Moreover, the plasma discharge chambers would need to be manufactured under high temperature, which increases the difficulty of alignment and processing costs. The plasma gas discharge AMLCD is operated at high voltages so that expensive driving circuits must be used.
It is, therefore, desirable to provide an improved AMLCD where the above-described difficulties are alleviated.